All ceramic oxygen-generating systems work in accordance with the same basic working principle. The ceramic electrolyte is bounded on either side by an electrode, that is, a cathode on one side (the air side) and anode on the other (the oxygen side). The ceramic electrolyte is preferably fabricated into a thin membrane in order to enhance oxygen flux and reduce internal resistance. Upon applying voltage across the electrolyte/electrode assembly oxygen molecules in the air side of the system are first ionized at the cathode/electrolyte interface (O.sub.2 +4e.sup.-.fwdarw.2O.sup.2-). The negatively charged oxygen ions, driven by the potential gradient, then diffuse through the electrolyte via a large number of existing vacancies. At the opposite anode/electrolyte interface, oxygen molecules are reformed after releasing electrons (2O.sup.2-.fwdarw.O.sub.2 +4e.sup.31). Since the ceramic electrolyte permits only O.sup.2- diffusion, pure oxygen is therefore generated on the oxygen side of the system.
Prior art ceramic oxygen generating systems typically use stabilized zirconia or ceria as an electrolyte material. Unfortunately, these ceramic oxygen-ion-conducting materials require a high temperature, in excess of 800.degree. C., in order to achieve satisfactory conductivity. The need therefore exists for a cost-effective materials system for ceramic oxygen generating applications at lower operating temperatures (below 800.degree. C.).
Recently, a new group of low-temperature ceramic ionic conductors has emerged, based on bismuth vanadate doped with metal cations. The highest conductivity has been exhibited by copper-doped bismuth vanadate, known by the generic name BICUVOX. BICUVOX generally has the following formula: Bi.sub.2 V.sub.0.9 Cu.sub.0.1 O.sub.5.35.
BICUVOX has high potential for use in ceramic oxygen generating systems operating at temperatures below 600.degree. C. One of the most significant benefits associated with the lowered working temperature is the availability of low-cost, machinable metals for use as electrodes.